This competitive supplement project will examine previously collected videotaped parent-adolescent communication interactions among dyads enrolled in Project STYLE: "HIV Prevention for Youth with Severe Mental Illness" (2R01, MH 63008-07). We are requesting additional funds to support this project given that there were major revisions to the originally proposed coding system in the parent application. Adolescents, particularly those in mental health treatment, are at risk for HIV because of sexual and substance use behaviors. Parent-child communication about sexual topics and parental supervision are associated with delays in the onset of sexual activity and more responsible sexual behavior (e.g., consistent condom use). The parent project, Project STYLE, is a randomized trial that is evaluating the comparative efficacy of the family- based intervention compared to the comparison conditions with respect to improving observed communication patterns among parents and adolescents over a 12-month follow-up period. This multi-site project (Rhode Island Hospital, Emory University and the University of Illinois at Chicago) has enrolled a diverse group of 721 adolescents in mental health treatment and their parents. Few studies have examined directly observed communication between parents and adolescents, especially this vulnerable and high-risk group, so this project videotaped parents and adolescents having a 5-minute discussion about a conflict topic prior to their intervention and at follow-up assessments. Within the on-going project an observational coding system (Dyadic Observational Communication System;DOCS) was developed, specifically for this project, to assess the quality of parent-teen communication during videotaped discussions. Codes of the DOCS were designed to match the behavior and interactive changes targeted by our family-based intervention (e.g. Negative and Positive Vocalizations and Relationship Quality). Examination of videotaped conversations will 1) further establish the reliability and validity of the DOCS 2) examine the impact of the family-based Project STYLE intervention on observational communication data 3) examine the relationship between changes in the DOCS codes over the 12-month follow-up period in relationship to adolescent sexual risk behavior over the 30-month extended follow-up period and 4) modify the Project STYLE family-based intervention based on data obtained from the observed communication data. Project STYLE has had excellent retention rates (>80%) and preliminary examination of the DOCS subscales indicates excellent inter-rater reliability and acceptable convergent validity. Public Health Significance: (1) Examine whether family-based HIV prevention programs can change communication patterns between parents and adolescents, which will then impact adolescent's sexual risk taking behavior. Parent-adolescent communication may serve as an important mediator between parent-adolescent relationships and adolescent sexual behavior. (2) Inform other prevention programs on how to effectively change communication between parents and adolescents to target sexual risk among adolescents. PUBLIC HEALTH RELEVANCE: Adolescents, particularly those in mental health treatment, are at risk for HIV because of sexual and substance behaviors. Parent-child communication about sexual topics and parental supervision are associated with delays in the onset of sexual activity and more responsible sexual behavior. This supplemental project will allow us to examine whether family -based HIV prevention programs, through examination of directly observed parent-adolescent communication, can change communication patterns between parents and adolescents, which will then impact adolescent's sexual risk taking behavior.